The MQM Flex GTX is part of Merrell’s newly-released fastpacking and trail running line. The other MQM (“Moving Quickly through the Mountains”) models include – from most to least protective – the MQM Flex Mid GTX ($170), MQM Flex Mid ($140), and low-top MQM Flex ($110). Compared to the rest of Merrell’s trail running line, the MQM Flex GTX is far and away the most durable and protective. It sits right above the Agility Peak, which is a flexible, versatile trail runner.  The most stripped-down trail shoes in Merrell’s line-up are the minimalist Bare Access and Trail Crusher models. Merrell is probably best-known for these minimalist trail runners (especially the discontinued Trail Glove) and their traditional hiking boots, so the MQM line sits right in between.

The MQM Flex GTX weighs 13.0oz (men’s size 9), which makes it the heaviest shoe in this round of testing (the next closest is the New Balance Hierro v3 at 11.9oz for men’s size 9). The heel-to-toe drop is also the highest at 10mm (30mm rear stack height, 20mm forefoot). That’s a substantial amount of sole underneath, but not as much as a maximalist trail runner like the Hoka Challenger ATR 4 (which weighs substantially less at only 9.0oz for men’s size 9). The heavier weight comes with some serious protection though. The MQM Flex GTX has a GoreTex waterproof liner, full-length midsole rockplate, full-coverage outsole with no exposed foam, and supportive uppers with heat-bonded overlays. According to Merrell, the MQM Flex GTX insole is also treated with an antimicrobial agent to reduce foot odor. That’s a unique feature that none of the other trail running shoes in this round of testing claim.

The runners in our wear-test team thought the MQM Flex GTX offered substantial protection from the trail, which is exactly what it was designed for.  However, it sacrifices agility, speed, and ride quality. Multiple wear-testers reported that the MQM Flex GTX feels sluggish and clunky on the trail, especially when they tried to pick up the pace. The outsole is protective in rocky terrain and has great traction in technical sections, but overkill for anything more tame. Overall, our team thought this could be a great choice for fastpackers or trail runners who spend a lot of time hiking through rocky mountain trails. Trail runners/fastpackers who are looking at the Salomon X-Ultra, North Face Hedgehog, or Salewa Mountain Trainer will want to have the Merrell MQM Flex GTX on their list, too.

Comfort

The MQM Flex GTX has a high-volume upper, probably to accommodate thick, well-cushioned hiking socks. With regular-weight running socks, the uppers felt voluminous. Some extra room in a shoe can be welcome, like the extra width Altra and Topo add across their toeboxes, but too much volume makes the shoe feel uncomfortable. That was the case here, according to our wear-test runners. However, they thought the materials of the upper were well-padded and comfortable. The tongue and heel collar are particularly cushioned and well-matched, which makes sense for a shoe designed for long, easy days on the trail. Far and away the biggest concern with comfort was the arch bump built into the insole. Every single wear-tester mentioned it in their review, and always negatively.  “The arch is obnoxiously high,” wrote one runner on our wear-test team. “It feels like running with half a basketball under your arch.” Another wear-tester agreed, noting, “the insole under the arch was particularly pronounced and positioned too far forward.” He was able to run comfortably in the shoes by swapping out the insoles, but runners with a new shoe shouldn’t immediately have to look for replacement parts. One summed up the group’s thoughts well with, “if not for the awkward arch, I would give the MQM Flex GTX a much high score for comfort since it’s well padded and well cushioned.”

Speed

The MQM Flex GTX is not built for speed the same way competitors like the Alpine XT or Salomon XA Elevate are. However, our wear-testers also compared the MQM Flex GTX negatively to other shoes on the heavier end of the spectrum like the New Balance Hierro v3 and Columbia/Montrail. As one wear-tester put it, “The MQM Flex GTX is not a fast shoe by any means. It’s stiff and heavy, feeling much more like a low-top hiker you can run in when need be, versus a dedicated running shoe.”  Another concluded, “After several runs in these, the midsole still feels stiff and clunky. This was most evident in turnover and footstrike. The midsole was fine for rock protection, but overall made the MQM Flex GTX a slow tank of a shoe.”

Security of Fit

The MQM Flex GTX’s uppers are a combination of breathable mesh and TPU overlays, which give the shoe a balance between ventilation and structure.  The heel counter is particularly firm, with a proprietary “Hyperlock” wraparound TPU bumper. In a narrower, more closely-fitting package, our wear-testers may have felt more secure in this shoe.  As it stands, the voluminous fit, wide heel and roomy forefoot make runners’ feet slide around inside the shoe. One of the runners on our wear-test team observed that, “moderately narrow feet can twist right out of the shoe with some effort, and the only remedy is to use the double set of eyelets near to the top of the tongue or a double-pull lacing.” Neither alleviates the bunched-up fabric in the toe box however.  The fit may work for some runners, however. As one of our wear-test team members noted, “I didn’t mind the wider forefoot because of the shape of my foot, but the heel was way too sloppy to get a secure fit, and the combination of the two would be hard to overcome for most runners.” Trail runners with particularly wide, high-volume feet or those who prefer to run in very thick socks may find that they don’t have any issues with the MQM Flex GTX’s fit.

Agility

Here our team was testing how well the MQM Flex GTX performs on a variety of different types of terrain and trail conditions. The MQM Flex GTX is designed to be a hybrid hiker/runner, and our wear-test team wasn’t surprised that it wasn’t as versatile as more multi-purpose shoes. In rocky, technical sections of trail, the MQM Flex GTX offers great protection from sharp edges, but doesn’t inspire confidence to run quickly.  On smooth rolling singletrack or gentle fire roads, the stiff sole and heavy weight were overkill and hard to run in. One of the runners on our wear-test team described the ride as “clunky and blocky, not supple or smooth.” Another concluded, “it does OK for hiking, but I’d never just go for a straight run in them.”

Responsiveness

The MQM Flex GTX’s firm midsole foam wasn’t squishy or unresponsive, and none of the runners on our team reported sinking into the soles or feeling like they were running on marshmallows. A firm sole can give great energy transfer between the body and shoe, with no wasted energy on takeoff or landing. However, the MQM Flex GTX’s midsole was stiff enough that the responsiveness was overshadowed by the clunky trail feel. As one of our wear-testers wrote, “a firm sole needs to have some flexibility so it doesn’t feel like you’re running on a foot-shaped block of wood. Unfortunately, that’s exactly how these felt.”

Protection

This was an area of strength for the MQM Flex GTX, which is no surprise.  “The big advantage of this shoe is that it’s very protective in rocky terrain,” praised one wear-tester.  The protective elements cover the whole shoe from bottom to top, as one of the other runners on our wear-test team pointed out.  He wrote, “this is where the MQM Flex GTX really excels, with excellent all-day protection in rocky, steep terrain and off-trail conditions. The upper is sturdy, as is the toe bumper, and the GoreTex lining adds another element of weather proofing in rain and snow.” One area of concern was the high-volume fit, which made some of our wear-test runners feel like their feet were rattling around inside the shoe. As one put it, “the MQM Flex GTX is protective, but more like a big cage than a secure cradle.”

Over the course of a few weeks, our wear-test team does multiple runs in each pair of shoes they test.  They aim for a variety of runs (easy recovery runs, long training runs, harder race-pace efforts) across as many different types of trails as they can manage.  The team is spread across the country, so we are able to test under a variety of different conditions, terrains, and types of trail, from gently-rolling fire roads to highly technical mountain singletrack.